(KARE) It’s impressive when someone finishes a marathon. Even more impressive, are those who run marathons year after year.

But a controversial study is raising questions about health benefits of distance running.

A Minneapolis heart doctor found that long-time marathoners have more plaque in their arteries than non-runners.

The study, published in Missouri Medicine, compared 50 men, who all ran the Twin Cities marathon 25 years in a row, to a control group of 25 non-runners, including men who were overweight, smokers or who had diabetes.